<style>
    ul {
        background-color: pink;
    }
    li {
        margin: 20px 0;
        background-color: green;
    }
    .tips{
        pointer-events:none;
        position: absolute; 
        width:100px;
        height:50px;
        background-color: yellow; 
        color:tomato;
        display:none;
    }
     #test{ 
        width:0; 
        height:0; 
        border-width:40px; 
        border-style:solid; 
        border-color:yellow transparent transparent; 
        font-size:0; 
        line-height:0;}
    
    </style>
    <ul>
        <li>001</li>
        <li>002</li>
        <li>003</li>
        <li>004</li>
        <li>005</li>
    </ul>
    <div class="tips">提示框</div>
    <script>
        var ulObj=document.querySelector("ul")
        ulObj.onmousemove=function(evt){
        var e=evt ||window.event
        var target = e.target||e.srcElement//获得当前操作的标签
        if (target.nodeName == 'LI' ){
            var tipsObj = document.querySelector('.tips')
            tipsObj.style.display = 'block' 
            tipsObj.style.left = e.clientX + 'px'
            tipsObj.style.top = e.clientY + 'px'
            tipsObj.innerHTML = target.innerHTML+'<div id="test"></div>'
        }
        }
    </script>
    